DETROIT -- Presidents Day promotions and a slight warm-up from January's unusually harsh winter weather may have helped U.S. auto sales improve this month, but probably not by much.

High inventories and rising incentives are raising questions about whether the auto industry has lost some of its momentum as the critical spring selling season draws near.

"We expect elevated incentive spending to continue," Larry Dominique, executive vice president of TrueCar, said in a statement. "March is going to be a 'must-win' month for dealers if they hope to have a successful 2014."

TrueCar estimates that February new-vehicle sales will rise just 0.5 percent from a year ago, to a seasonally adjusted annualized rate of 15.4 million. That compares with a SAAR of 15.2 million last month, when snowstorms and subzero temperatures across large swaths of the country dampened showroom traffic, and 15.3 million in February 2013.

Cars.com also expects a 15.4 million SAAR, with volume up 1 percent.

Alec Gutierrez, senior analyst at Kelley Blue Book, is forecasting flat sales overall, with General Motors and Ford Motor Co. posting the biggest declines among major automakers because the worst weather has been in parts of the country where they are most popular.

Sales in California and other warmer areas that tend to buy foreign brands have been "very robust," he said. He projected a SAAR of 15.3 million.

"There's still a lot of research activity -- a lot of folks out there looking to buy," Gutierrez told Automotive News, citing steady traffic on KBB's Web site and increased sales activity during the lulls between snowstorms. "Once the rest of the country kind of thaws out and gets through these ongoing cold snaps, we should see the market bounce back."

Soft fleet demand

In addition to inclement weather, Barclays Capital analyst Brian Johnson said today that soft fleet shipments have had a negative impact on light-vehicle volumes this month.

He estimates that sales will rise 0.9 percent to 1.21 million, and that the SAAR will come in at 15.5 million units.

"The pace of sales in the final week of the month will likely be dictated by weather and incentive spending," Johnson said.

LMC Automotive is more optimistic about February, projecting a year-over-year sales increase of 3 percent and a SAAR of 15.7 million. It said retail sales would rise 5 percent.

"Although severe weather impacted sales in early February, the negative effect should be somewhat mitigated since the majority of vehicle sales occur in the second half of the month," John Humphrey, senior vice president of the global automotive practice at J.D. Power, which provides the registration data used in LMC's forecast, said in a statement.

Richard M. Kwas, senior analyst with Wells Fargo Securities, said the industry SAAR will reach "the high 15 million range" this month and could surpass 16 million in March, which has five weekends. The monthly SAAR has topped 16 million only twice -- last August and November -- since 2007.

"According to our industry sources, vehicle sales were stronger than expected during the Presidents Day weekend," Kwas wrote in a report on Friday. "We expect a strong push to close February."

Automakers will report February sales on Monday March 3.

Incentives climbing

Incentives have risen 3 percent since January and 5 percent since February 2013, according to TrueCar, which lists increases of more than 20 percent year-over-year for American Honda, Hyundai-Kia Automotive, Toyota Motor Sales U.S.A. and Volkswagen Group of America.

The data show incentive spending up 16 percent from a year ago at Ford but down at GM and Chrysler Group.

Beyond the added discounts, dealers in large parts of the nation's snow belt say they have not been able to do much this winter to attract more shoppers.

"When it's snowing an inch an hour, there's not many people out there looking at stickers. They're online looking at the cars," said Duke Macgrayne, new-car sales manager at Fox Ford in Grand Rapids, Mich. "We've had over 100 inches of snow so far, and we've had 11 or 12 weeks of winter, so do the math."

Group 1 Automotive last week warned that its first-quarter earnings would be lower than anticipated because snow and ice caused "significant" disruptions at 105 of its 118 U.S. stores.

Although sales are not growing as quickly as they have in recent years, LMC is predicting average transaction prices will reach a record of more than $29,000 this month, beating the record set in February 2013 by more than $400 per vehicle.

LMC said it still expects full-year U.S. sales of 16.2 million, but it reduced its North American production forecast by 100,000 units to 16.5 million, which would be a 2.5 percent decline from 2013.

Automakers started February with an 88-day supply of vehicles, the highest for the date since 2009, when the industry's sales downturn hit bottom.

LMC said inventories should thin out in the spring but that production levels in the second half of the year could decline further if a hefty backlog remains through June.

"With the likelihood of fleet sales holding below 18 percent and modest retail sales increases, the absolute rate of growth could be lower than initially expected," said Jeff Schuster, LMC's senior vice president of forecasting. "The auto industry needs to be prepared for slower but stable growth and increased competitive intensity, which will put pressure on the successful execution of launches this year."

TrueCar's forecast shows Chrysler and Nissan North America gaining market share this month from a year ago, with Ford and GM each losing 1.2 percentage points. It expects share for other major automakers to remain essentially flat.